title: Effects of exercise and lifestyle modification on fitness, insulin resistance, skeletal muscle oxidative phosphorylation and intramyocellular lipid content in obese children and adolescents.
abstract: BACKGROUND
  Obesity is associated with poor fitness and adverse metabolic consequences in children.
  
  
  OBJECTIVE
  To investigate how exercise and lifestyle modification may improve fitness and insulin sensitivity in this population.
  
  
  METHODS
  Randomized controlled trial, 21 obese (body mass index ≥ 95% percentile) subjects, ages 10 to 17 years.
  
  
  METHODS
  Subjects were given standardized healthful lifestyle advice for 8 weeks. In addition, they were randomized to an in-home supervised exercise intervention (n = 10) or control group (n = 11).
  
  
  METHODS
  Fasting laboratory studies (insulin, glucose, lipid profile) and assessments of fitness, body composition, skeletal muscle oxidative phosphorylation and intramyocellular lipid content (IMCL), were performed at baseline and study completion.
  
  
  RESULTS
  Subjects were 13.0 ± 1.9 (standard deviation) years old, 72% female and 44% non-white. Exercise improved fitness (P = 0.03) and power (P = 0.01), and increased IMCL (P = 0.02). HOMA-IR decreased among all subjects in response to lifestyle modification advice (P = 0.01), regardless of exercise training assignment. In univariate analysis in all subjects, change in cardiovascular fitness was associated with change in HOMA-IR. In exploratory analyses, increased IMCL was associated with greater resting energy expenditure (r = 0.78, P = 0.005) and a decrease in fasting respiratory quotient (r = -0.70, P = 0.02) (n = 11).
  
  
  CONCLUSIONS
  Change in fitness was found to be related to change in insulin resistance in response to lifestyle modification and exercise in obese children. IMCL increased with exercise in these obese children, which may reflect greater muscle lipid oxidative capacity.
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA; Division of Endocrinology, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, USA; Division of Endocrinology and Diabetes, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: McCormack
authors.forename: M A
authors.initials: MA
authors.lastname: McCarthy
authors.forename: S G
authors.initials: SG
authors.lastname: Harrington
authors.forename: L
authors.initials: L
authors.lastname: Farilla
authors.forename: M I
authors.initials: MI
authors.lastname: Hrovat
authors.forename: D M
authors.initials: DM
authors.lastname: Systrom
authors.forename: B J
authors.initials: BJ
authors.lastname: Thomas
authors.forename: M
authors.initials: M
authors.lastname: Torriani
authors.forename: K
authors.initials: K
authors.lastname: McInnis
authors.forename: S K
authors.initials: SK
authors.lastname: Grinspoon
authors.forename: A
authors.initials: A
authors.lastname: Fleischman
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000378:metabolism; D002648:Child; D003924:Diabetes Mellitus, Type 2 / Q000517:prevention & control*; D004038:Diet, Reducing; D015444:Exercise; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D050356:Lipid Metabolism; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D010085:Oxidative Phosphorylation; D010349:Patient Compliance; D063766:Pediatric Obesity / Q000378:metabolism* / Q000503:physiopathology / Q000517:prevention & control; D010807:Physical Endurance; D010809:Physical Fitness; D040242:Risk Reduction Behavior; D014481:United States
chemical_list: D015415:Biomarkers
keywords: IMCL; mitochondrial function; paediatric obesity